The present invention relates to ink jet printers. In particular, the invention relates to ink jet printers having large-volume ink reservoirs mounted at a location remote from the print carriage.
Ink jet printers and disposable ink jet cartridges for ink jet printers are well known in the art. Contemporary disposable ink jet cartridges typically include a self-contained ink reservoir, a jet plate assembly supporting a plurality of ink jet nozzles in combination with the ink reservoir and a plurality of external electrical contacts for connecting the ink jet nozzles to driver circuitry. Typically, the entire cartridge must be disposed of when the ink in the cartridge reservoir is used up without regard to whether or not the jet plate assembly remains fully functional.
For a thermal ink jet printer which contains multiple ink outlet nozzles, failure is usually caused by the failure of the resistors used to heat the ink in proximity to each nozzle. Due to relatively low resistor failure rates, the jet plate assemblies used in the currently available disposable ink jet cartridges are fully operable to their original print quality specifications after the original ink reservoir has been depleted. The contemporary disposable cartridge therefore represents a considerable waste of product resulting in higher costs to the consumer both in product cost and the time involved in having to frequently replace the cartridge.
Merely making the ink jet cartridge reservoir larger in size is not a satisfactory solution to problems associated with frequent replacement of or refilling of the ink jet cartridge. The ink jet cartridges are generally mounted on the moving print carriage of the ink jet printer. Therefore, the larger the volume of ink in the ink jet cartridge, the greater the amount of weight that is required to be moved by the printer carriage holding the ink jet cartridges. The additional weight of ink in the ink jet cartridges will cause significant demands on the motor that drives the printer carriage. Performance is also limited by heavier print carriages because a larger carriage inertia must be overcome at the two endpoints of carriage motion. At these locations, the carriage reverses direction to begin another pass over the media during the printing process. Increased carriage inertia increases the time required to reverse direction for a given drive motor size, and therefore can reduce print speed.
In addition, ink jet cartridges are typically mounted on one side of the print carriage and cause an unbalanced load which requires a counter balancing mechanism. Therefore, it is difficult to provide a larger volume of ink in the ink jet cartridges to limit the number of times that the cartridges need to be refilled with the power consumption and loading problems that larger ink volumes cause.
As a result, it is known in the art to manually replenish the ink within the disposable ink jet cartridge during the time period when the print quality from the jet plate is known to be high, but the original ink in the ink jet cartridge has been depleted. Manually refilling the disposable ink cartridges is, however, messy and difficult because many disposable ink jet cartridges are not designed with refilling in mind. More recently, some ink jet cartridges have been designed to enable refilling, such as the ink jet cartridge disclosed by in U.S. Pat. No. 5,280,300. These refillable ink jet cartridges are designed to enable refilling of the ink jet cartridge for a certain number of refills while the jet plate is still providing high quality printing capabilities. Making the cartridge easy to refill, however, does not mitigate the bother, time, and expense involved in having to refill this cartridge frequently.
Automatic refilling has also been contemplated. In U.S. Pat. No. 4,967,207 to Ruder, a system is disclosed which allows periodic refilling of the ink-jet cartridge at a xe2x80x9cservice stationxe2x80x9d provided at one extreme of carriage movement. In addition, various schemes of continuously supplying ink to the small reservoir in the disposable ink-jet cartridge from a larger reservoir located remote from the print carriage have been proposed. For example, U.S. Pat. No. 4,831,389 to Chan discloses large volume ink supplies connected through supply tubes to a foam containing ink-jet cartridge. The ink is continuously supplied to the ink-jet cartridge through capillary action as the ink in the cartridges is depleted.
U.S. Pat. Nos. 5,369,429 and 5,367,328 describe a system including a typical ink jet cartridge having an ink reservoir and a jet plate assembly mounted on a printer carriage, and an external reservoir system which refills the ink reservoir in the ink jet cartridge during printing. In the system disclosed in U.S. Pat. No. 5,369,429, the external ink reservoir, the ink jet cartridge, and the tubing connecting the external reservoir to the ink jet cartridge are configured to form a unitary single piece replaceable assembly. The volume of ink in the external reservoir is designed to be depleted when the print quality of the jet plate on the ink jet cartridge assembly has degraded to a level that may provide unsatisfactory printing results.
Systems such as those disclosed by U.S. Pat. No. 5,369,429, require the disposal of a large ink reservoir, an ink jet cartridge, and the tubing connecting the two once the ink in the large reservoir has been depleted. The waste and initial cost to the consumer therefore still exists for this type of system. Moreover, as the concerns over disposal of large quantities of plastic goods increases, such bulky disposable systems are not desirable. In addition, the unitary plastic assembly becomes contaminated by the ink and may not be suitable for conventional disposal. Also, the replacement of the unitary one-piece unit of the system described in U.S. Pat. No. 5,369,429 is difficult due to the size of the ink reservoir. Further, the tubing attached to the reservoir must be installed in the printer with care to ensure that it is properly positioned so as to not interfere with the moving parts of the printer.
A system using refillable remote ink reservoirs is available from VIP Systems in Belgium. This type of system helps alleviate the waste problems discussed above. In addition, the VIP Systems device is made almost entirely from clear plastic, allowing a certain degree of operator monitoring of ink level. However, as with the devices described in U.S. Pat. No. 5,369,429, this system is installed external to the printer housing and ink seepage and spills can interfere with operator monitoring of ink level. Also, the VIP Systems device incorporates a relatively complex priming system to remove air from the tubes when new ink-jet cartridges are installed. The complexity and external attachment of the VIP Systems device therefore renders it more expensive to produce and rather difficult to use.
The present invention is an ink jet printer which provides a continuous volume of ink to the moveable print carriage without suffering from the inconvenience of use, waste, cost and cumbersome disposal problems of the prior art systems. Advantageously, the inking system comprises a plurality of small removable ink jet cartridges, each in fluid communication with a different one of a plurality of large ink reservoirs permanently mounted substantially within an end housing of the ink jet printer. Flexible tubing also permanently mounted within the ink jet printer connects each large reservoir to each ink-jet cartridge to enable the print carriage to move back and forth while maintaining a connection from the ink reservoir to the ink jet cartridge. The permanently mounted ink reservoir can be refilled with ink from time to time for the entire lifetime of the ink jet printer without needing to be replaced.
The ink-jet printer of the present invention provides substantial advantages over prior art systems because the large volume ink reservoirs are substantially internal to an end housing of the printer itself. Preferably, the large volume ink reservoirs are xe2x80x9cpancakexe2x80x9d shape, with width smaller than height and depth, and several are stacked horizontally in the end housing. This allows efficient use of space, and convenient means for expanding the number of large volume ink reservoirs provided with a printer.
Another significant feature of a preferred embodiment of the invention is that the level of ink in each large reservoir is conveniently visible from the front of the ink jet printer even though the reservoirs are substantially internal to the end housing. In one embodiment, a transparent portion of the large ink reservoirs is external to the end housing, while the remainder of the reservoir is internal to the housing. This feature renders the monitoring of the level of ink in each reservoir especially easy and convenient for the operator of the printer. Preferably, a transparent integral ridge provided on each of the large volume ink reservoirs comprises the portion of the reservoir which is external to the end housing. In this embodiment, the ridges protrude through vertical slots in the end housing, thereby also functioning to hold the reservoirs in place inside the housing.
Furthermore, when an ink-jet cartridge needs to be replaced because the cartridge has a finite life span during which the print quality is satisfactory, only the ink-jet cartridge needs to be replaced. The ink jet cartridge is removably mounted to the tubing via a quick disconnect fitting to enable easy replacement of the ink jet cartridge. Removal of the ink jet cartridge does not require the removal of other portions of the ink system. Therefore, the replacement of a cartridge is easy for the user and does not require replacement of other tubing or the large volume ink reservoir whose viable lifetime is much greater than that of the jet plate assembly. Thus, the ink supply system of the present invention substantially reduces waste, cost and disposal problems while providing a large volume of ink to the printer and maintaining high quality printing.
Advantages are also provided because the production cost of a preferred embodiment of the present invention is minimized by allowing ink to feed from the large volume reservoirs to the ink-jet cartridges by a siphon action through the connecting tubes, eliminating the need for pumps or pressure regulating devices. In this embodiment, the large volume ink reservoirs and their visible, ink level monitoring portions are positioned such that the level of ink in the large volume reservoirs changes from about two to about nine inches below the level of ink in the print cartridge as the reservoir is depleted from approximately full to approximately empty.
A further advantage of the invention is that the ink reservoir is refillable using simple procedures and is located such that refilling of the ink reservoir does not interfere with other moving parts of the ink jet printer. In addition, the ink reservoir is refillable during the normal operation of the printer, i.e., printing does not have to be halted in order to refill the ink reservoir.